Antislip sheet material having tapes and monofilaments

ABSTRACT

A sheet material with an anti-skid surface, suitable for use as a roofing underlayment or wrapper, comprises a scrim made of woven plastic tapes with monofilaments that are round in cross-section and have a diameter larger than the thickness of the plastic tapes interwoven with the tapes. The monofilaments form ridges on the sheet material that impart an enhanced coefficient of friction to it. The monofilaments may be incorporated in the weave in the warp or weft directions or both.

TECHNICAL FIELD OF THE INVENTION

The invention pertains to sheet materials made of plastic tapes,suitable for roofing, wrapping and other applications. Moreparticularly, it pertains to such sheet materials having a surface witha high coefficient of friction.

BACKGROUND OF THE INVENTION

Sheet materials comprising a scrim of woven plastic tapes are commonlyused for roofing and wrapping applications. The sheet materials may becoated or uncoated. Such materials typically have a relatively smoothsurface with a low coefficient of friction. For some applications, it isuseful for the sheet material to have antislip properties. For example,if the sheet is to be applied to a roof deck, e.g. as a roofingunderlayment, a surface with antislip properties on which workers maywalk enhances worker safety. Likewise, if the sheet material is to beuse to wrap goods such as bundles of lumber, on which workers may needto walk, an antislip surface is useful. The conventional methods ofimparting antislip properties to sheet materials involve applying films,meshes or granules to the surface of the sheet.

SUMMARY OF THE INVENTION

The invention provides a sheet material comprising a scrim made of wovenplastic tapes which incorporates filaments, for example monofilaments,cords, wires, string, rope or burlap strings, inserted in the weave inthe warp or weft or both directions, the filaments being round incross-section and having a diameter larger than the thickness of theplastic tapes, forming ridges on the sheet material that impart anenhanced coefficient of friction to it. The sheet material providesenhanced slip-resistance in wet, dry or dusty conditions. The sheetmaterial is useful for applications such as industrial wrapping,packaging and roofing underlayment.

According to one embodiment of the invention, there is provided a sheetof material having an anti-skid surface, comprising a first set of tapesgenerally parallel to each other, a second set of tapes generallyparallel to each other and perpendicular to the first set of tapes, thetapes of the two sets being interwoven with each other to form a scrim.The tapes are extruded plastic having a width greater than theirthickness. Filaments, for example monofilaments, generally parallel tothe first set of tapes are positioned on the tapes of the first set andinterwoven with the tapes of the second set. The filaments are round incross-section and have a diameter greater than the thickness of thetapes and form ridges on the surface of the sheet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a sheet according to one embodiment of theinvention.

FIG. 2 is a plan view of a detail of the sheet.

FIG. 3 is a cross-sectional view on the line 3-3 of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Exemplary embodiments are illustrated in the referenced figures of thedrawings. It is intended that the embodiments are to be consideredillustrative rather than restrictive.

The sheet material 30 has a scrim 32 coated on one side by a coatinglayer 34. The scrim 32 is woven in a plain weave of warp tapes 36 andweft tapes 38. Warp monofilaments 40 and weft monofilaments 42 areincorporated into the structure of the scrim 32. In particular, the warpmonofilaments 40 are positioned on respective warp tapes 36 and areinterwoven with the weft tapes 38; and the weft monofilaments 42 arepositioned on respective weft tapes 38 and are interwoven with the warptapes 36 and with the warp monofilaments 40. This produces a grid 44 ofwoven monofilaments on one side of the scrim 32. The appearance of thesheet 30 is accordingly that of two overlapping woven scrims, one madeof tapes and one of monofilaments. The warp and weft tapes 36, 38provide the overall strength of the fabric and they hold themonofilament grid 44 in position.

In the illustrated embodiments, the warp and weft monofilaments arepositioned every fourth warp or weft tape, respectively. Alternatively,they may be positioned on every second, or third, etc. tape, or atselected other spacings.

The thickness of the tapes 36, 38 is typically about 1-2 mils (0.025 to0.05 mm). The thickness (i.e. diameter) of the monofilaments 40, 42 isabout 10-30 mils (0.25 to 0.76 mm), for example about 15 mils. Themonofilaments accordingly produce ridges on the surface of the scrim 32,running in both the warp and weft directions, which provide an increasedcoefficient of friction to the sheet 30.

To form an effective anti-skid surface, the height of the ridges shouldbe at least about six times greater than the thickness of the tapes,alternatively at least about twenty times greater. For purposes ofclarity of illustration, in FIGS. 2 and 3 the thickness of the tapes 36,38 is exaggerated; it is to be understood that the monofilaments formridges of substantial thickness, relative to the much smaller thicknessof the tapes 36, 38.

The monofilaments are woven in such a way that the weft monofilaments 42pass under the warp monofilaments 40, as best seen in FIG. 2. Thisresults in the warp monofilaments 40 being raised at their points ofintersection, increasing the height of the ridges at those points. Thedenier of the monofilaments and the spacing of the monofilaments in theweave can be varied to achieve the desired coefficient of friction.

The scrim 32, coating 34 and tapes 36, 38 are made of plastic,preferably polyolefin resins, for example polyethylene or polypropylene.They may alternatively be made of various other plastics, includingpolyesters, polystyrene, nylon and ethylene acrylic copolymers. Thetapes 36, 38 and/or the coating 34 may alternatively comprise a highcoefficient-of-friction material, for example ethylene vinyl acetate(EVA), ethylene methyl acrylate (EMA), rubber or elastomer. Themonofilaments are generally round in cross-section and can likewise bemade of any suitable plastic, including the same plastics as the rest ofthe sheet.

The tapes 36, 38 are preferably about 1.5 to 6 mm in width. The numberof tapes per inch in the machine direction and in the cross direction ispreferably in the range of 1 to 25.

The coating layer 34 (shown in FIGS. 2 and 3) is a waterproof filmbonded to the scrim. It may be permeable to water vapor to allow theescape of moisture from buildings when the sheet is used as a roofingunderlayment or for similar applications. The coating layer 34 ismanufactured in-situ using an extrusion process and is laminated to thescrim 32, or it can comprise a film that is bonded to the scrim, forexample by thermal bonding, lamination or adhesive. Optionally, a secondcoating layer is bonded to the opposite side of the scrim.

In embodiments of the sheet materials of the invention, the sheet can beuncoated, coated on one side or on both sides, or it can includeadditional layers, or can include monofilaments in only the warpdirection or only the weft direction or in both directions. The color ofthe monofilaments can be the same as the surrounding tapes to blend inor it can be pigmented to make the antislip grid visible. Themonofilaments or the coating, or both, can be treated with or comprise atacky or high coefficient-of-friction coating or additive, for example,EVA, EMA, rubber or elastomer. These choices depend on the propertiesdesired for a particular application.

In other embodiments of the invention, filaments other thanmonofilaments 40 are used. Examples of suitable materials include cords,wire, string, rope and strings of burlap. For purposes of recyclabilityof the sheet material, it is desirable that the filaments and the tapesbe of the same composition, or at least of plastics material that can berecycled together. Accordingly, plastic monofilaments are preferred tothese alternative materials.

Although the invention has been described in terms of variousembodiments, it is not intended that the invention be limited to theseembodiments. Various modifications within the scope of the inventionwill be apparent to those skilled in the art. The scope of the inventionis defined by the claims that follow.

1. A sheet of material having an anti-skid surface, comprising: a firstset of tapes generally parallel to each other; a second set of tapesgenerally parallel to each other and perpendicular to the first set oftapes; the tapes being extruded, flat plastic tapes having a widthgreater than their thickness; the tapes of the first set and of thesecond set being interwoven with each other to form a scrim; a first setof plastic monofilaments generally parallel to the first set of tapes,each said monofilament of the first set of monofilaments beinginterwoven with the tapes of the second set of tapes; the monofilamentsof the first set being generally round in cross-section and having adiameter at least six times greater than the thickness of the tapes andforming anti-skid ridges on the surface of the sheet; and a waterprooffilm bonded to the scrim.
 2. A sheet according to claim 1, furthercomprising a second set of plastic monofilaments generally parallel tothe second set of tapes, each said monofilament of the second set ofmonofilaments being interwoven with the tapes of the first set of tapesand the monofilaments of the first set of monofilaments; themonofilaments of the second set being generally round in cross-sectionand having a diameter greater than the thickness of the tapes andforming anti-skid ridges on the surface of the sheet.
 3. A sheetaccording to claim 1, wherein the tapes of the first set are warp tapes.4. A sheet according to claim 1, wherein the tapes of the first set areweft tapes.
 5. A sheet according to claim 1, wherein the scrim is aplain weave.
 6. (canceled)
 7. A sheet according to claim 1, wherein themonofilaments have a diameter at least twenty times greater than thethickness of the tapes.
 8. A sheet according to claim 1, wherein thethickness of the tapes is about 1 to 2 mils.
 9. A sheet according toclaim 1, wherein the diameter of the monofilaments is about 10 to 30mils.
 10. A sheet according to claim 1, wherein the tapes have a widthin the range of 1.5 to 6 mm.
 11. A sheet according to claim 1, whereinthe tapes and monofilaments comprise polyolefin.
 12. A sheet accordingto claim 1, wherein the tapes and monofilaments comprise one or more ofpolyethylene, polypropylene, polyester, polystyrene, nylon or ethyleneacrylic polymer.
 13. A sheet according to claim 1, wherein themonofilaments have a color that contrasts with the color of the tapes.14. A sheet according to claim 1, wherein the monofilaments comprise atacky or high coefficient-of-friction material.
 15. A sheet according toclaim 1, wherein the film comprises a tacky or highcoefficient-of-friction material.